This invention has relation to travel trailers which are adapted to be combined with auxiliary utility trailers in such a way as to support the entire combination on one central set of wheels.
It is known to support auxiliary boat trailers on the main frame of a house trailer or travel trailer. In the patents to Bledsoe, U.S. Pat. No. 3,649,064 granted Mar. 14, 1972 and U.S. Pat. No. 3,651,969 granted Mar. 28, 1972, an auxiliary trailer is backed in between a pair of spaced-apart tracks projecting rearwardly from the house trailer, the front end of the auxiliary trailer is supported with respect to the ground while the auxiliary trailer is coupled to the rear portion of the house trailer and the wheels on the auxiliary trailer are cranked up off of the ground. When it is desired to tow the trailer separately, while the trailers are still coupled together, a support is provided at the trailer tongue end of the auxiliary trailer in order that the auxiliary trailer wheels can be mechanically cranked down toward the ground, and then the front support remains in place until the two trailers are uncoupled from each other at which point a towing vehicle can back into the auxiliary trailer to be hitched and the support of the auxiliary trailer at the trailer tongue end is no longer necessary.
The idea of supporting a utility trailer between a towing vehicle and a boat trailer is disclosed in U.S. Pat. No. 3,751,073 to Alexander et al, granted on Aug. 7, 1973. This patent shows a "piggy back extension 30" between the front end of a boat trailer and the rear end of another vehicle. To load the small utility trailer 54 onto the piggy back extension 30, trailer 54 is backed into place over the towing end of the extension. After the utility trailer 54 is hooked to a trailer hitch at a front portion of the piggy back extension, the piggy back extension and the utility trailer are lifted apparently by main force to get high enough so that the extension can be hitched to the towing vehicle.
U.S. Pat. No. 3,380,607 granted to Dale on Apr. 30, 1968 shows the broad idea of supporting a boat on a rear portion of the main frame of a trailer where a housing unit or main closure is supported on a forward portion of the trailer. There are no separate wheels on the trailer to support the boat, and when we have to back the entire trailer including the housing unit down to the water's edge or beyond in order to get the boat on and off.
Also cited as of general interest by a skilled searcher are U.S. Pat. No. 3,463,590 granted to Crate on Dec. 14, 1982; U.S. Pat. No. 4,626,162 granted to Parisi on Dec. 1, 1986; and U.S. Pat. No. 4,705,278 granted to Weber on Nov. 10, 1987. These patents are not believed to be particularly pertinent to the concept of the present invention.